- Polygon (Wikipedia)
In geometry, a polygon (/ˈpɒlɪɡɒn/) is a plane figure made up of line segments connected to form a closed polygonal chain.
- In geometry, a polyhedron (pl.: polyhedra or polyhedrons; from Greek πολύ (poly-) ‘many’, and ἕδρον (-hedron) ‘base, seat’) is a three-dimensional shape with flat polygonal faces, straight edges and sharp corners or vertices.
- Tetrahedron (Wikipedia)
In geometry, a tetrahedron (pl.: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertices. The tetrahedron is the simplest of all the ordinary convex polyhedra.